Fresh and frozen food items are shipped worldwide by food suppliers. The fishing industry is one food supplier which ships tremendous quantities of fresh and frozen fish. The fish are often shipped from remote locations in areas such as Alaska to virtually every corner of the world. To preserve the quality of the fish, great care must be taken to avoid spoilage. Warm temperature contributes greatly to spoilage. Salmon in particular is one delicacy which must be handled with great care to preserve its delicate flavor. Thus, in shipping salmon, it is important to maintain frozen fish at a temperature at or below 32.degree. F. and fresh fish at a temperature of between 33.degree. F. and 38.degree. F. It is also important to prevent the fish from either drying out or sitting in water.
Fish are shipped in many types of containers. Many such containers utilize corrugated paperboard in their construction. One version provides a layer of metallized plastic film adhered to the corrugated paperboard. These containers are usually configured to have a top half placed over a bottom half. To help maintain the desired temperature within the container, it is typical for refrigerants such as dry ice or reusable ice packs to be placed within the container. However, even the use of these refrigerants does not consistently maintain the temperature within conventional containers for extended periods of time, such as up to six days under the unrefrigerated conditions often encountered during shipment.
In conventional containers, temperature change is generally attributable to conductive heat transfer between the inner and outer panels of the container, convective air flow into and out of the container, conduction due to condensation formed as the result of ambient air entering the container and contacting the cooler air within the container, and radiant heat transfer. For example, when shipping cold contents, air circulation between the inside of the container and the outside of the container is detrimental to temperature maintenance. Conduction between the inner panels and the outer panels of the container and from condensation can also cause temperature change. In addition to warming both the air and the contents within the container, condensation wets the container material and weakens its structural integrity, degrades the contents, and leaks from the container. Leakage from the container is highly undesirable to air carriers, because the leakage often contains substances corrosive to the airplane. For example, in addition to mess and damage from condensation which is primarily water, the water can also mix with the contents, including salt, blood, and fish slime, to create a highly offensive and corrosive ooze.
It has been suggested to wrap the contents within the container in insulation, such as insulation consisting of mineral wool and paperboard glued together and then glued between a pair of plastic sheets, or to otherwise place insulation within the container to maintain the temperature within the container. This, however, does not inhibit conduction between panels or prevent air from passing into and out of the container. One packaging method uses tape, glue or the like to seal the container such that air is prevented from entering or exiting the container. This, however, does not inhibit conduction between the panels of the container and detracts from the container's ability to be reused. It is also known to provide a metallic or reflective finish on containers to reduce radiant heat transfer. However, these metallic finishes can promote conductive heat transfer if surfaces having a metallic finish are placed in close proximity to other surfaces having a metallic finish.
Thus, there is a need in the art for an improved method for insulating shipping containers and for an improved, reusable insulated shipping container which inhibits the passage of air into and out of the container, inhibits the formation of condensation within the container, prevents liquids from entering into or escaping from the container, decreases conduction between panels of the container, and reduces radiant heat transfer.